The present program is a follow up research on 48 mother-infant dyads studied when the infants were 6 months old and 24 of the same sample were studied at 4/5 years old about the transition between dyadic affective regulation and infant affective self regulation (UBACyT P806). A theoretical revision on the role of play in psychic development is included. Microanalysis showed differences between face to face interaction and free play interaction at 6 months regarding infant's self-regulatory resources. We also found a relationship between the variables maternal self esteem and reflective function in the mothers, and the exploratory play behaviors observed in the infants. These results underscore the role of play with toys as mediating factor in the transition from dyadic affect regulation to affective self-regulation.